acl, qacl: split off shared functions into separate object file
Some of the helper functions in file-has-acl.c are used from qcopy-acl.c while
file_has_acl() isn't needed there. Split the shared functions off into
acl-internal.c.
* lib/file-has-acl.c: Remove helper functions here.
* lib/acl-internal.c: Add helper functions here.
* modules/qacl: Use acl-internal.c instead of file-has-acl.c here.
* modules/acl: Add file-has-acl.c now that qacl doesn't use it anymore.